Triathlon models started appearing from the major manufacturers around 1983/1984. Apollo were made by Kuwahara who used an open format serial number, So if the first two numbers are 1984, then it was manufactured in 1984, though if it was manufactured late in the year it could be a 1985 model. I believe the 3rd and 4th digits should represent the month of manufacture.

Most triathlon models were mid-range models and this seem to fit the bill, with a 4130 frame and the component mix. I don't have any Apollo literature for the era but it was probably about 3rd from the top of the line and around $400 US. Nice bicycle and it appears to be in very good condition. Congratulations on your acquisition.

Cambio Rino was an Italian brand imported by Jim Gardin. They are notable in that they also manufactured their own components, which were featured on many of their models.